Roll forming apparatus for metallic strip, and method



y 15, 1958 A. D. WILEY ETAL 2,843,179

ROLL FORMING APPARATUS FOR METALLIC STRIP, AND METHOD 7 Filed May 23, 1955 United States Patent ROLL FORIVIING APPARATUS FOR METALLIC STRIP, AND METHOD Allen Dale Wiley and Roy Vogal Russell, Middletown,

Ohio, assignors to Armco Steel Corporation, Middletown, Ohio, a corporation of Ohio Application May 23, 1955, Serial No. 510,191 4 Claims. (Cl. 153--77) engaged when the strip is formed into a helix so as to form a helical lock scam in the formed pipe.

The apparatus of the present invention is particularly useful in place of the somewhat similar roll forming apparatus of the Freeze patents, Nos. 2,136,942 and 2,136,943, dated November 15, 1938.

In accordance with the teachings of the said Freeze patents, metallic strip from a coil passes through a roll forming apparatus which forms a series of longitudinal corrugations of the strip and forms at one edge a flange element and at the other end a hook element. The strip is fed into a forming 'die at an angle to the axis thereof and is bent upwardly and around into a helix, such that the hook element along one edge of the strip engages over the flange element along the other edge of the strip and which edges come together at the end of the first convolution. The interengaged hook and flange elements, according to the Freeze disclosure, are then compressed together and gradually inclined and folded down against the body of the formed pipe and finally tightly compressed to form a helical lock seam.

- According to the disclosure of the Freeze patents, the first pair of rolls of the forming apparatus form a single valley centrally of the strip. Additional roll stands then added valleys on either side of the central valley until most of the width of the strip was corrugated and the last pair of rolls of the machine added a flange along one edge and a hook element along the other edge.

We have found that when strip was progressively formed as taught in the Freeze patents, unequal forming stresses were applied by the flanging'rolls because greater deformation was involved in forming the hook element than in forming the, flange element.

It is an object of the present invention, in the light of the above outlined situation, to provide a roll forming machine wherein substantially equal stresses are produced by each set of forming rolls, so that the hook element along one edge of the strip is not subjected to greater forming stresses than the flange element along the other edge of the strip. It is a further object of the invention to provide a roll forming machine for preparing metallic strip for the ultimate formation into helical lock seam pipe which will provide for a more uniform and stronger lock seam than has heretofore been possible.

These and other objects of our invention, which will be pointed out in greater detail hereinafter, we accomplish by that certain construction and arrangement of parts of which we shall now disclose an exemplary embodiment.

Reference is made to the drawings forming a part hereof and in which:

Figures 1 to 7 represent fragmentary elevational views through successive pairs of forming rolls showing how the strip is progressively deformed.

Briefly, in the practice of our invention, we depart from the teachings 'of the Freeze patents by forming in the first roll stand a corrugation crest. To put it in an other way, we make our first deformation ofl-center toward that side of the strip along which the hook portion will ultimately be formed by a distance equal to one-half the pitch of the corrugations.

In the second roll stand, we then add one crest to each side of the first crest. In the third stand, we add an additional crest on each side. In the fourth roll stand, weadd a still further crest to each side. In the fifth roll stand, we add the final crest on that side which will be provided with the flange and in formgig the final crest,

we partially form the flange while at the other side of the strip we partially form the hook element. In the sixth roll stand, we continue with the formation of both the flange and hook elements and in the seventh roll stand, we complete the formation of the hook and flange elements. In this way, the forming stresses in any given roll stand are substantially equal on both sides of the strip and the hook element is not subjected to an excessive draw.

Referring now in greater detail to the drawing, the

first pair of forming rolls are indicated at 10 and 10a.

The strip'being formed is indicated at 11 and the center line of the finished strip is indicated at 12. According to the Freeze teachings, the first pair of forming rolls would have been centered on the center line 12 and, instead of producing a downwardly directed crest, would have produced an upwardly directed valley. The inversion referred to results from the fact that the strip is ultimately bent upwardly to form the helix so that the underside of the strip forms the exterior surface of the pipe, so that the corrugation 13 in the formed pipe will be a crest.

In the second roll stand, as seen in Figure 2, we provide the roll pair 20 and 20a which adds the crests 14, one on either side of the crest 13. In Figure 3, the roll stand comprises the roll pair 30, a and this adds the additional crests 15 on either side of the crests 14.

In the roll stand of Figure 4, we have the roll pair 40, a which adds the crests 16 on either side of the crests 15.

In Figure 2, we show the fifth roll stand comprising the roll pair 50, a in which the final corrugation 17 is added on the left side which will be the flanged edge, and we partially form the flange as indicated at 18. Along the other edge of the strip, we partially form the hook element as indicated at 19. Thus, after the fifth roll stand all of the corrugations have been formed and the hook portion has been partially formed as well.

In the sixth roll stand, shown in Figure 6 and comprising the roll pair and 60a, we continue the formation of the flange as indicated at 21 and we continue the formation of the hook element as shown at 22.

In the final roll stand, shown in Figure 7 and comprising the roll pair and 70a, we complete the formation of the flange element 23 and of the hook element 24. At this point then the strip is completely formed and ready to pass into the forming die where it will be bent into a helix and wherein the flange 23 will be caused to engage within the hook portion 24 and wherein the seam will be compressed, laid down and clinched.

From the foregoing description, it will be clear that the hook portion 24 during its formation has not been subjected to an excessive draw and that its formation has been balanced in part by the formation of the corrugation 17 at the opposite edge of the strip.

With this roll forming machine more uniform and more perfect lock seam is insured in the finished pipe.

Also the balanced design will cause the strip to track in' a uniform manner through the stands, even in the case of camber.

It will be understood that minor modifications may be made without departing from the spirit of the invention and we, therefore, do not intend to limit ourselves otherwise than as set forth in the claims.

Having now fully described our invention, What we claim as new and desire to secure by Letters Patent is:

l. A roll forming apparatus for preparing metallic strip for formation into helical lock seam pipe, comprising a l plurality of stands of complementary forming rolls, the rolls of the first stand adapted to produce a first longitudinal corrugation, the rolls of a number of succeeding stands each adapted to produce an additional corrugation on each side of said first corrugation, a further succeeding stand having rolls adapted to produce a single corrugation adjacent one edge and to partially form a hook element along the other edge, and additional stands having rolls adapted to complete the formation of said hook element, and to form a flange along the edge opposite said hook element.

2. A roll forming apparatus for preparing metallic strip for formation into helical lock seam, comprising seven stands of complementary forming rolls, the rolls of the first stand adapted to produce a first longitudinal corrugation, the rolls of the second, third and fourth stands each adapted to produce an additional corrugation on each side of said first corrugation, the fifth stand having rolls adapted to produce an additional corrugation adjacent one edge and to partially form a hook element along the other edge, the sixth stand having rolls adapted to continue the formation of said hook element and to partially form a flange element along the edge opposite said hook element, and the seventh stand having rolls adapted to complete the formation of said hook and flange elements.

3. A method of preparing metallic strip for the formation of helical corrugated lock seam pipe, which includes the steps of continuously forming a first corruga, tion then forming successively an equal number of additional corrugations on each side of said first corrugation, then partially forming a hook element along one edge of said strip While forming the final corrugation adjacent the opposite edge, and then concurrently completing the formation of said hook element and forming along said opposite edge a flange element.

4. A method of preparing metallic strip for the formation of helical corrugated lock seam pipe, which includes the steps, in the formation of an even number of longitudinal corrugations, of first forming a single corrugation adjacent but off-center of the strip, successively adding equal numbers of longitudinal corrugations on each side of said single corrugation, concurrently partially forming a hook element along one edge of said strip and forming a final corrugation adjacent the opposite edge, and finally concurrently completing the formation of said hook element and forming along said opposite edge a flange element.

References Cited in the file of this patent UNITED STATES PATENTS 1,485,917 Harter Mar. 4, 1924 1,766,743 Freeze June 24, 1930 2,136,942 Freeze Nov. 15, 1938 2,339,219 Crowley Jan. 11, 1944 FOREIGN PATENTS 7 23,709 Germany Aug. 29, 1883 

